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J. P. GARDNER.

Sun Dial. No. 3.370. Patented Dec. 5,1843.

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JAMEs P. GARDNER, or coLUMBIA, TENNESSEE.

SUN-DIAL.

. Specification of Letters Patent No. 3,370, dated December 5, 1843. H

To all whom it may concern:

7 Be it known that I, JAMES P. GARDNER, of

Columbia, inthe county of Maury and State of Tennessee, have invented anImproved Mode of Constructing Sun-Dials, of which the followingis aspecification.

The drawing marked A, represents a hemispherical dial four inches indiameter, with the sun shining upon it at 2 oclock p. m.

C, represents a gnomon in a conical shape about one third of an inch indiameter at the bottom and tapering to a point. The

gnomon is based in the center of the concave hemisphere and its pointison an exact level with the margin of the dial, so that when the sunrises the shadow made by the point of the gnomon will strike the marginof the dial, on the opposite side, and as the sun rises higher andhigher the shadow will sink lower and lower along the side of. the dialtracing a regular line with its point from west toeast until the settingofthe sun when the point of the shadow will strike the.

margin of thedial in the east.

D, represents the shadow of the gnomon with its point just crossing theline which terminates at figure 2, and it is that figure which denotesthe hour of the day when the point ofthe shadow crosses that line, andso in like manner when the point of the shadow reaches theline whichterminates at of the base of the gnomon and terminating at E representsan exact north and south line passing from the margin of the dialthrough the center, along the concave surface to the point E. l

E represents the south pole, and is the point to which all the north andsouth lines converge, and the same lines continued north would convergeat the north pole.

The line running from figure 7 west represent a line onthe surface ofthe dial running from 7 through and along the concave surface to figure5 andis the line which will be traced by the point of the gnomons shadowfrom figure 5 to figure 7 when the sun rises at 5 oclock and sets at 7oclock. The line running from figure 6 west, represents a line on theconcave surface of the dial which will be traced by the point of thegnomons shadow when the sun rises at 6 oclock and sets at 6 oclock. Inlike manner as to the line running from figure 5 west &c. The other twolines commencing at figure 13 and 11 and running west are intended toshowthe length of the days when the point of the gnomons shadow tracesthose lines.

The lines which runfrom figures 12, 1, 2, 3, 4, 5, 6, 7 south allrepresent lines which are drawn upon the concave surface of the dialfrom the point E dividing the equinoctial line, running east and westfrom figure 6 to figure 6, into twelve equal parts, and-the figuresrepresent the twelve equal parts or hours into which a day is divided,when the shadow of the gnomons pointwtnacesmthe equinoct-ial line. Theselines may be increased in number so as to represent half or quarterhours &c.

In laying off or marking the dial the latitude of the place for whichthe dial is designed must first be ascertained. This is done by a simplecalculation, and by the use of the dividers. The dial from whichthedrawing is made is prepared for the latitude of Washington City. Thelatitude is found by measuring the number of del grees on the north andsouth line running equatorial or equinoctial line through this 7 pointof latitude. This is a simple process effected by the use of thedividers by setting one foot of the dividers on the north and southlines at a point just as far north of the point designated by letter Eas the latitude is north of the gnomons center.

Having thus laid down the equinoctial line, the next process is todivide this line into as many equal parts as are desired to representhours or fractions of an hour.

This is done by striking lines With the dividers and in this Way theWhole dial is completed.

I claim The mode herein described of constructing sun dials that is tosay, using therefor a hemispherical cup, having the lines laid off uponits inner surface in the manner described, and the gnornon in the centerof the cup arising from its bottom all as hereln 10

